A man breathes through an oxygen mask as another one receives treatments, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib, Syria April 4, 2017. REUTERS/Ammar Abdullah

Suspected chemical attacks killed at least 100 people in Syria’s rebel-held northwestern province of Idlib on Tuesday and left another 400 suffering from respiratory problems, a Syria medical relief group said.

The death toll is likely to rise, according to the Union of Medical Care Organizations, a coalition of international aid agencies that funds hospitals in Syria and which is partly based in Paris.

The group said the village of Khan Sheikhoun to the south of Idlib had initially been hit before strikes on the White Helmets emergency services centre in Khan Sheikhoun and the Al-Rahme hospital.

“We have seen more than 40 strikes since 06h30,” it said. “The toll continues to increase as do the strikes in the Idlib region as well as non-chemical attacks in Hama,” the group said.